1. Field of the Invention
The present invention relates generally to PC to host communications, and more particularly to terminal emulation on a PC for communications with an IBM mainframe or minicomputer.
2. Description of Related Art
Today's enterprise features universal personal and network computing. In most cases the same enterprise is a long-term user of and investor in International Business Machines Corp. (Armonk, N.Y.) ("IBM") host computing systems and technology. In the early 1980s, the arrival of the Personal Computer (PC) in IBM host computing environments created a PC-to-IBM host connectivity market. Today this hardware/software market is approximately a $1 billion segment of the networking industry.
The PC-to-IBM host connectivity market has gone through several transitions over the past decade. In the early 1980s the market formed around the replacement of Control Unit Terminals ("CUT mode devices") with hardware/software combinations such as the "IRMA" card. The first major transition in this market began in 1985 with IBM's introduction of distributed function terminal ("DFT") mode in its cluster controllers (3X74), terminals, and modified PCs. PC-to-host connectivity vendors responded by developing DFT mode software for PC-DOS, an effort which required development of complete SNA protocol engines.
By the late 1980s many organizations were swept up in the process of connecting PCs together into Local Area Networks (LANs). This gave rise to another transition in the market, the connections of LAN-attached PCs to IBM hosts. The use of connectivity methodologies that deny PCs powerful access to local and wide area networks (such as coax/twinax to fixed function cluster controllers) is on the decline, being replaced by gateway and direct connect configurations that treat IBM hosts as one of several internetwork servers.
In 1990 the transition in the Intel PC install base to Windows 3.X began. Windows is a product of Microsoft Corp. (Redmond, Wash.). The effect upon the IBM host connectivity market was immediate and profound. New, high growth companies emerged that specialized in Windows-to-IBM host connectivity. For the first time, changes in the desktop computing environment begat significant changes in the use of IBM host computers.
In the typical PC-DOS-to-IBM host connectivity installation, terminal emulation software allows operation of the PC as a dual function device: both PC-DOS application processor and host terminal. The typical PC-DOS based 3270 or 5250 product may also include other features for host connectivity such as application programming interfaces and/or file transfer software. However, the limitations of PC-DOS itself (memory management and user interface in particular) hinder general development and deployment of more powerful PC-to-host connectivity systems.
The widespread adoption of Windows 3.X on Intel Desktop PCs created a market for more innovative PC-to-IBM host connectivity software. Graphical User Interface technology has been applied to the task of simplifying the look and feel of older host applications. Enhanced mode memory management allows for more reliable deployment of underlying PC-to-host communications technology such as Advanced Program to Program Communications/Logical Unit ("APPC/LU") 6.2 engines. Task switching enables the concurrent use of various PC-to-host applications and services on a single desktop. All of these innovations represent incremental improvement over the DOS-to-IBM host computing environment.
One important aspect of IBM host connectivity is host data incorporation. Host data incorporation can generally be broken down into two approaches: screen scraping based on the High Level Language Application Programming Interface "(HLLAPI") applications programming interface ("API"), and client/server systems based on APPC/LU 6.2. HLLAPI allows users to write high level language programs for automating repetitive tasks and console operations. It also allows for masking complex applications from the user, consolidating several tasks into one simple task, monitoring tasks without human intervention and simplifying existing host applications.
In coding HLLAPI applications, the corporate developer is presented with at least two alternatives. One is to write a traditional Windows application in C that reads and writes from the host display session presentation space as needed to incorporate host display session data into Windows applications. Another is to write a Visual Basic application that includes Visual Basic custom controls that perform a similar set of encapsulated host presentation space read/write functions and services. Both methods may consume anywhere from a few days to a few months worth of development effort, depending upon the complexity of the data incorporation problem and the skill of the developer.
Although IBM host applications can be written having a more contemporary user interface, most IBM host applications are old, and it is difficult to make significant changes to them. These older IBM host applications are commonly known as "legacy applications." One defining characteristic of legacy applications is that they are navigated linearly and sequentially. Thus, where some IBM host applications may be accessed using Software Query Language ("SQL"), legacy applications typically cannot. Furthermore, SQL access is generally limited to relational database management systems ("RDBMSs").
Yet, although the legacy applications are old, the data stored with them and typically accessible only through them can be quite new and relevant. Thus, despite the age of the legacy applications, there continues to be a great need to use them.
It is therefore a first object of the invention to provide simplified navigation of IBM host applications. It is also an object of the invention to provide simplified navigation of IBM host applications using a PC-based terminal emulator. It is a further object to simplify for users the task of incorporating data from an IBM host application into a Windows applications. It is a further object to provide a system in which a network administrator or IS professional can build software relationships that facilitate such data incorporation. Other objects of the invention are to provide these other objects in an economical fashion requiring a minimum of modification to legacy applications and IBM hosts.
These objects and others are provided by the screen navigation method of the present invention.